Process for the production of water-soluble fluorine-containing vinyl ethers

ABSTRACT

The present invention relates to a method for producing a water-soluble fluorine-containing vinyl ether which comprises subjecting a fluorine-containing 2-alkoxypropionic acid derivative represented by the following general formula (I): 
                         
(wherein A represents —OM 1  or —OM 2   1/2 , and M 1  represents an alkali metal and M 2  represents an alkaline earth metal; X represents a halogen atom; Y 1  and Y 2  are the same or different and each represents a fluorine atom, a chlorine atom, a perfluoroalkyl group or a fluorochloroalkyl group; n represents an integer of 0 to 3, and n of Y 1 s may be the same or different; m represents an integer of 1 to 5, and m of Y 2 s are the same or different; and Z represents a hydrophilic group) to thermal decomposition at a temperature of not lower than 50° C. but lower than 170° C. in the presence of a coordinating organic solvent to give a water-soluble fluorine-containing vinyl ether represented by the general formula (II):
 
                         
(wherein Y 1 , Y 2 , Z, n and m are as defined above),
         said coordinating organic solvent having a coordinating property with an ion of said M 1  or an ion of said M 2      said coordinating organic solvent being in an amount of 10 to 1,000 parts by mass per 100 parts by mass of the fluorine-containing 2-alkoxypropionic acid derivative.

CROSS-REFERENCE TO RELATED APPLICATION

This Application is 371 of PCT/JP03/07592 filed Jun. 16, 2003.

TECHNICAL FIELDS

The present invention relates to a method for producing a water-soluble fluorine-containing vinyl ether from fluorine-containing 2-alkoxypropionic acid derivatives in good yields.

BACKGROUND ART

Hydrophilic group-terminated fluorine-containing vinyl ethers can be used, either as such or after protection of the terminal hydrophilic group by fluorination or by esterification, amidation or imidation, for the production of copolymers by polymerization with another fluoroolefin and/or the like.

The copolymers obtained can have salt-forming hydrophilic groups and, therefore, the use thereof as ion exchange membranes in salt electrolysis, chemical sensors, separation membranes, fuel cells and so forth is under investigation. They can also be utilized as superstrong acid catalysts in the form of powders as such, or in lithium cells and so on.

As a method for obtaining water-soluble fluorine-containing vinyl ethers, there is disclosed, in WO 98/43952 pamphlet, a thermal decomposition method which comprises heating, for decarboxylation, a fluorine-containing 2-alkoxypropionic acid derivative with carboxyl group being in the form of a metal salt. This thermal decomposition method known in the art has a problem in that a side reaction occurs, namely oligomers are formed from the fluorine-containing 2-alkoxypropionic acid derivative.

As regards the reaction conditions for this thermal decomposition, WO 01/28989 pamphlet discloses that the reaction should preferably be carried out at 170 to 230° C. using 1 to 5 parts by weight of a catalyst having a coordinating property with a metal ion per 100 parts by weight of the fluorine-containing 2-alkoxypropionic acid derivative.

Under such conditions, however, the byproduct oligomers are formed in large amounts and the yield of the desired product thus decreases. In carrying out the reaction on a large scale using a large-sized reactor, in particular, a long time is required for raising the temperature and for lowering the temperature, whereby the production of oligomers further increases. Thus, there is a problem that such conditions are difficult to apply on a commercial scale.

The water-soluble fluorine-containing vinyl ethers, which are the target products to be obtained by this thermal decomposition reaction, occur as high-boiling salts and, therefore, the distillation method cannot be used as the method of purifying them. A promising method is recrystallization. However, it is not easy to crystallize the water-soluble fluorine-containing vinyl ethers in the presence of a large amount of oligomers, which are uncrystallizable and thus render the purification by recrystallization difficult to achieve.

SUMMARY OF THE INVENTION

In view of the above-discussed state of the art, it is an object of the present invention to provide a method for producing a water-soluble fluorine-containing vinyl ether in good yields from fluorine-containing 2-alkoxypropionic acid derivatives.

The present invention relates to a method for producing a water-soluble fluorine-containing vinyl ether which comprises subjecting a fluorine-containing 2-alkoxypropionic acid derivative represented by the following general formula (I):

(wherein A represents —OM¹ or —OM² _(1/2), and M¹ represents an alkali metal and M² represents an alkaline earth metal; X represents a halogen atom; Y¹ and Y² are the same or different and each represents a fluorine atom, a chlorine atom, a perfluoroalkyl group or a fluorochloroalkyl group; n represents an integer of 0 to 3, and n of Y¹s may be the same or different; m represents an integer of 1 to 5, and m of Y²s are the same or different; and Z represents a hydrophilic group) to thermal decomposition at a temperature of not lower than 50° C. but lower than 170° C. in the presence of a coordinating organic solvent to give a water-soluble fluorine-containing vinyl ether represented by the following general formula (II):

(wherein Y¹, Y², Z, n and m are as defined above),

said coordinating organic solvent having a coordinating property with an ion of said M¹ or an ion of said M² and

said coordinating organic solvent being used in an amount of 10 to 1,000 parts by mass per 100 parts by mass of the fluorine-containing 2-alkoxypropionic acid derivative.

In the following, the present invention is described in detail.

DETAILED DISCLOSURE OF THE INVENTION

The method for producing a water-soluble fluorine-containing vinyl ether comprises subjecting a fluorine-containing 2-alkoxypropionic acid derivate represented by the above general formula (I) to thermal decomposition.

The fluorine-containing 2-alkoxypropionic acid derivative represented by the above general formula (I) is such one that A in the above general formula (I) represents —OM¹ or —OM² _(1/2), wherein M¹ represents an alkali metal and M² represents an alkaline earth metal. The alkali metal M¹ is not particularly restricted but includes, among others, Li, Na, K and Cs. The alkaline earth metal M² is not particularly restricted but includes, among others, Mg and Ca. Preferably, A is —OM¹, and M¹ is Na, which is commercially inexpensive.

In the above general formula (I), X represents a halogen atom. The halogen atom is not particularly restricted but may be any of fluorine, chlorine, bromine and iodine atoms.

In the above general formula (I), Y¹and Y² are the same or different and each represents a fluorine atom, a chlorine atom, a perfluoroalkyl group or a fluorochloroalkyl group. The perfluoroalkyl group is not particularly restricted but maybe, for example, a trifluoromethyl group or a pentafluoroethyl group. The fluorochloroalkyl group is not particularly restricted but may be, for example, a difluorochloromethyl group. Preferably, Y¹ is a trifluoromethyl group and Y² is a fluorine atom.

In the above general formula (I), n represents an integer of 0 to 3. The n of Y¹s may be the same or different. For the fluorine-containing 2-alkoxypropionic acid derivative having a lot of hydrophilic groups per unit weight thereof, the above-mentioned n is preferably 0 or 1, more preferably 0.

In the above general formula (I), m represents an integer of 1 to 5. The m of Y²s may be the same or different. As the above-mentioned m increases, the acid strength increases but the number of the hydrophilic groups per unit weight of the fluorine-containing 2-alkoxypropionic acid derivative decreases. Therefore, the above-mentioned m is preferably 2.

In the above general formula (I), Z represents a hydrophilic group. The hydrophilic group is not particularly restricted but may be, for example, —COOM³, —OSO₃M³, —SO₃M³, —O₂PM³, —OP (OM³)₂, —O₂P (OM³), —OPO (OM³)₂, —PO₂ (OM³), —PO(OM³)₂, —COOM⁴ _(1/2), —OSO₃M⁴ _(1/2), —SO₃M⁴ _(1/2), —O₂PM⁴ _(1/2), —OP (OM⁴ _(1/2))₂, —O₂P (OM⁴ _(1/2)), —OPO (OM⁴ _(1/2))₂, —PO₂ (OM⁴ _(1/2)), —PO (OM⁴ _(1/2))², or a substituted ammonio group forming a salt with a conjugate base of an inorganic acid or fatty acid (its substituents being two or three alkyl groups which may be the same or different).

The above-mentioned M³ represents an alkali metal or hydrogen atom or NR¹R²R³R⁴, and R¹, R², R³ and R⁴ are the same or different and each represents a hydrogen atom or an alkyl group containing 1 to 4 carbon atoms. The alkali metal includes, among others, those given above by way of example referring to M¹. The above-mentioned M⁴ is an alkaline earth metal, and the alkaline earth metal includes, among others, those given above by way of example referring to M².

The term “substituted ammonio group” as used herein means a group constituted of a nitrogen atom and two or three alkyl groups, which are the same or different and are covalently bound to that nitrogen atom at sites other than the site represented by —(CFY²)_(m)— in the above general formula (I).

The substituted ammonio group is not particularly restricted but may be —NR⁵R⁶H or —NR⁵R⁶R⁷ (in which R⁵, R⁶ and R⁷ may be the same or different and each represents an alkyl group), for instance. The above substituted ammonio group forms a salt with a conjugated base of a monobasic or polybasic inorganic acid or fatty acid. The inorganic acid is not particularly restricted but includes, among others, hydrochloric acid, phosphoric acid, sulfuric acid and nitric acid. The fatty acid is not particularly restricted but includes, among others, formic acid, acetic acid and propionic acid.

In the above general formula (I), Z is preferably —SO₃M³ or —SO₃M⁴ _(1/2), more preferably —SO₃M³, still more preferably —SO₃Na.

The fluorine-containing 2-alkoxypropionic acid derivative represented by the above general formula (I) is preferably one in which, in the above general formula (I), Z is —SO₃M³, A is —OM¹ or —OM² _(1/2), Y¹ is a trifluoromethyl group, Y² is a fluorine atom and m is 2. More preferably, in the above general formula (I), Z is —SO₃Na, A is —Ona, X is a fluorine atom, Y² is a fluorine atom, n is 0 and m is 2.

The method for preparing the fluorine-containing 2-alkoxypropionic acid derivative represented by the above general formula (I) is not particularly restricted but, for example, any of the methods known in the art can be employed. Among the fluorine-containing 2-alkoxypropionic acid derivatives represented by the above general formula (I), those compounds represented by the following general formula:

(wherein X, Y¹, Y², n, m, M¹ and M² are as defined above) can be obtained by neutralizing or saponifying the corresponding compounds represented by the following general formula:

(wherein A¹ represents an alkoxyl group or a halogen atom, A² represents a halogen atom; X, Y¹, Y², n and m are as defined above) using a neutralizing reagent.

The method for producing a water-soluble fluorine-containing vinyl ether according to the present invention comprises subjecting a fluorine-containing 2-alkoxypropionic acid derivative represented by the above general formula (I) to thermal decomposition in the presence of a coordinating organic solvent to give the corresponding water-soluble fluorine-containing vinyl ether represented by the general formula (II).

The coordinating organic solvent has a coordinating property with the ion of the above-mentioned M¹ or the ion of the above-mentioned M². In the method for producing a water-soluble fluorine-containing vinyl ether according to the present invention, the above coordinating organic solvent exhibits a decarboxylation reaction-promoting catalytic action by coordinating the ion of M¹ or the ion of M² which the fluorine-containing 2-alkoxypropionic acid derivative of the above general formula (I) has.

The coordinating organic solvent is not particularly restricted but may be any of those having a coordinating property with an ion of M¹ or an ion of M². Preferably, it comprises an aprotic polar organic solvent. The aprotic polar organic solvent is not particularly restricted but includes, among others, ether solvents, sulfolane, hexamethylphosphoric triamide, acetonitrile, dimethylformamide, dimethyl sulfoxide, ethyl acetate, tetramethylurea and the like. One or two or more of these may be used singly or in combination.

The ether solvent is not particularly restricted but includes, among others, glyme-based compounds, diethyl ethers, diisopropyl ethers, tetrahydrofuran, dioxane, anisole, and crown ethers. These may be used singly or two or more of them may be used in combination.

The above-mentioned glyme-based compounds are hydrocarbon-based ether compounds represented by the general formula: R—O

CH₂CH₂—O

_(q)R wherein R represents —C_(p)H_(2p+1), p represents an integer of 1 to 5 and q represents an integer of 1 to 10.

As the above-mentioned glyme-based compounds, there may be mentioned dimethoxyethane, monoethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether and diethoxyethane, among others. These may be used singly or two or more of them may be used in combination.

The above-mentioned aprotic organic polar solvent is preferably a glyme-based solvent, more preferably diethylene glycol dimethyl ether.

Preferably, the aprotic polar organic solvent has a water content not exceeding 250 ppm so that the yield of the water-soluble fluorine-containing vinyl ether may be increased. The aprotic polar organic solvent is required to have the water content within the above range only at least on the occasion of thermal decomposition. More preferred is diethylene glycol dimethyl ether with a water content not exceeding 250 ppm.

In cases where a low-boiling solvent such as ethyl acetate or tetrahydrofuran is used as the coordinating organic solvent, such equipment as a pressure reaction apparatus becomes necessary for carrying out the thermal decomposition reaction at a temperature not lower than the boiling point of such solvent; however, the purification of the water-soluble fluorine-containing vinyl ether is easier than in the case of using a glyme-based solvent.

In carrying out the thermal decomposition in the practice of the present invention, the coordinating organic solvent itself may be used also as a dispersion medium. It is also possible, however, to use an inert solvent together with the coordinating organic solvent. Preferred as the inert solvent are fluorocarbons, which can be readily dehydrated, so that the yield of the water-soluble fluorine-containing vinyl ether may be increased. The fluorocarbons are not particularly restricted but include, among others, fluorocarbons and fluorochlorocarbons, which may be etherified. Among them, perfluorocarbons and perfluorochlorocarbons are preferred. The inert solvent may comprise one single species or two or more species.

The coordinating organic solvent is used in an amount of 10 to 1,000 parts by mass per 100 parts by mass of the fluorine-containing 2-alkoxypropionic acid derivative. Within the above range, the thermal decomposition initiation temperature becomes low, hence the byproduct formation can be suppressed. When that amount is less than 10 parts by mass, the thermal decomposition reaction may proceed slowly and/or the thermal decomposition may proceed only to an unsatisfactory extent. When the amount exceeds 1,000 parts by mass, a large reaction vessel becomes necessary and this is disadvantageous from the industrial viewpoint. A preferred lower limit is 30 parts by mass, and a preferred upper limit is 300 parts by mass.

The method for producing a water-soluble fluorine-containing vinyl ether according to the present invention is characterized in that the above-mentioned fluorine-containing 2-alkoxypropionic acid derivative is subjected to thermal decomposition at a temperature not lower than 50° C. but lower than 170° C. in the presence of the above-mentioned coordinating organic solvent to give the corresponding water-soluble fluorine-containing vinyl ether represented by the general formula (II).

When the thermal decomposition according to the present invention is carried out at temperatures not lower than 170° C., byproducts are formed in large amounts. The byproducts have not yet been clearly identified but probably are, among others, oligomers represented by the formula:

(wherein k represents an integer of 2 to 15, and Y¹, Y²,Z, n and m are as defined above) as formed by the reaction of the fluorine-containing 2-alkoxypropionic acid derivative with the water-soluble fluorine-containing vinyl ether or by the mutual reaction of molecules of the water-soluble fluorine-containing vinyl ether. As the byproduct formation increases, the yield of the water-soluble fluorine-containing vinyl ether decreases. In particular, when the reactor size increases, a long time is required for raising and lowering the temperature and, accordingly, the water-soluble fluorine-containing vinyl ether is exposed to high temperatures for a prolonged period of time, with the result that the byproduct formation is still increased.

As for the method of purifying the water-soluble fluorine-containing vinyl ether, recrystallization may be a promising method. Since, however, the byproducts are not crystallizable, it is difficult to crystallize the water-soluble fluorine-containing vinyl ether in the presence of a large amount of such byproducts.

When, in carrying out the thermal decomposition according to the present invention, the temperature is lower than 50° C., time is required for the thermal decomposition or the thermal decomposition may fail to proceed, although the byproduct formation mentioned above can be suppressed. The thermal decomposition is preferably carried out at a temperature not lower than 50° C. but lower than 150° C. Preferably, the thermal decomposition is carried out after thoroughly drying, for dehydration, the fluorine-containing 2-alkoxypropionic acid derivative and catalyst, and the inert solvent to be used if desirable.

The thermal decomposition reaction time in the practice of the present invention is preferably 10 to 600 minutes after arrival at the intended reaction temperature, although it depends on the temperature at which the thermal decomposition is carried out. If the reaction time is shorter than 10 minutes, the thermal decomposition may be incomplete. A more preferred lower limit is 30 minutes, and a more preferred upper limit is 300 minutes.

In the practice of the present invention, the fluorine-containing 2-alkoxypropionic acid derivative preferably has a water content not exceeding 0.1% by mass. When the water content is higher than 0.1% by mass, the fluorine-containing 2-alkoxypropionic acid derivative reacts with the water in certain cases to give, as a byproduct, a compound represented by the general formula:

(wherein X, Y¹, Y², Z, n and m are as defined above) and, accordingly, the yield of the water-soluble fluorine-containing vinyl ether tends to decrease. It is only required that the fluorine-containing 2-alkoxypropionic acid derivative has a water content within the above range at least on the occasion of carrying out the thermal decomposition.

The water-soluble fluorine-containing vinyl ether obtained by the method for producing a water-soluble fluorine-containing vinyl ether according to the present invention is represented by the above general formula (II) given herein above. In the above general formula (II), Y¹, Y², Z, n and m are as defined herein above referring to the above general formula (I).

According to the method of the present invention, byproduct formation can be inhibited by subjecting the fluorine-containing 2-alkoxypropionic acid derivatives to thermal decomposition at a temperature not lower than 50° C. but lower than 170° C. using the above-mentioned coordinating organic solvent, therefore the water-soluble fluorine-containing vinyl ethers can be obtained in good yields from the fluorine-containing 2-alkoxypropionic acid derivatives.

The water-soluble fluorine-containing vinyl ethers can be polymerized, either as such or after protection of the terminal hydrophilic group by fluorination or by esterification, amidation or imidation, together with another fluoroolefin, for instance, to give copolymers.

The copolymers obtained, which have salt-forming hydrophilic groups, can be adequately used as electrolyte membranes such as ion exchange membranes or diaphragms. As for the ion exchange membranes, they can be utilized in salt electrolysis, chemical sensors, separation membranes, fuel cells and so forth. The copolymers obtained can also be used as macromolecular superstrong acid catalysts in the form of powders as such, or in lithium cells or the like, in the form of liquids.

BEST MODES FOR CARRYING OUT THE INVENTION

The following examples illustrate the present invention in further detail. These examples are, however, by no means limitative of the scope of the present invention.

PRODUCTION EXAMPLE 1 Synthesis of a Fluorine-Containing 2-alkoxypropionic Acid Derivative

-   1.1) A 6-liter glass-lined pressure-resistant autoclave was charged     with SO₃ (2 liters) freshly prepared by distillation of Sulfan     (stabilized sulfuric anhydride; product of Nisso Metallochemical     Co.), the inside space atmosphere was purged with pure nitrogen gas     for substitution therewith, and tetrafluoroethylene was then charged     into the autoclave under pressure, upon which the exothermal     reaction started immediately. The reaction was continued while     maintaining the temperature at 40-60° C. and the pressure at 0.1 to     0.2 MPa. After 40 minutes, when the product amount increased to 5.2     liters and the absorption of tetrafluoroethylne was no longer     observed, the reaction was terminated by cooling. The reaction     product was a colorless, transparent liquid, which, upon     distillation, was found to be almost pure tetrafluoroethane     β-sultone. -   1.2) A 6-liter glass-lined pressure-resistant autoclave was charged     with 400 g of potassium fluoride thoroughly dried at 300° C. and     then tightly closed under nitrogen streams. Then, 1 liter of     diethylene glycol dimethyl ether was charged into the autoclave, and     the sultone (1 liter) obtained in the step 1.1) was added dropwise.     A marked exothermic reaction took place, and it was confirmed by     ¹⁹F-NMR analysis that the isomerization reaction to FSO₂CF₂COF had     been completed almost quantitatively although the formation of free     FSO₂CF₂CF₂OK was also observed. -   1.3) The product FSO₂CF₂COF obtained using the same reaction     apparatus and conditions as used in the step 1.2) was added, under     pressure at −10° C., and hexafluoropropylene oxide [HFPO] gas was     added to a pressure of 0.2 MPa, whereupon the exothermal reaction     started immediately. While the temperature was adjusted to −15 to     −5° C., the reaction was continued at a pressure of 0.1 to 0.2 MPa     for 3 hours. Thereafter, the rate of pressure dropping decreased, so     that the reaction was interrupted, and the residual gas was     discharged. The volume of the product was 2.7 liters, and the     product consisted of a yellow upper phase and a colorless lower     phase. Upon distillation, 90% by volume of the product was found to     be the HFPO (one mole) adduct, namely the compound:     FSO₂CF₂CF₂OCF (CF₃) COF.     In addition, the formation of a slight amount of FSO₂CF₂COF and the     HFPO (two moles) adducts was observed. -   1.4) The compound obtained in the step 1.3) was neutralized with a     20% (by mass) aqueous solution of sodium hydroxide for quantitative     conversion to the corresponding fluorine-containing     2-alkoxypropionic acid derivative. Thus was obtained a 36% (by mass)     aqueous solution of a compound represented by the formula:     NaOC (O) CF (CF₃) OCF₂CF₂SO₃Na.

The aqueous solution obtained was removed of the insoluble NaF by filtration and then dried at 80° C. for 36 hours and then further at 120° C. for 12 hours.

EXAMPLE 1

A 20-liter glass vessel equipped with a stirrer was charged with the fluorine-containing 2-alkoxypropionic acid derivative NaOC(O)CF(CF₃)OCF₂CF₂SO₃Na (6.4 kg) obtained in Production Example 1 and 5.3 kg of diethylene glycol dimethyl ether (83 parts by mass per 100 parts by mass of the fluorine-containing 2-alkoxypropionic acid derivative). The vessel was heated by means of a mantle heater. Upon arrival of the inside temperature at 100° C., the generation of CO₂ started. The inside temperature was then slowly raised to 140° C. After 180 minutes of heating, the CO₂ generation subsided and, therefore, the heating was discontinued. Pure water (6 liters) was added to the reaction mixture obtained for dissolving the same, the insoluble sodium fluoride was filtered off, and the remaining diethylene glycol dimethyl ether layer was extracted with 7 portions of chloroform to give an aqueous solution.

The thus-obtained aqueous solution was subjected to ¹⁹F-NMR spectrometry, and a comparison was made between the large peak at about −83.3 ppm (relative to CDCl₃) due to the underlined fluorine atoms of —OCF ₂CF₂— in the water-soluble fluorine-containing vinyl ether CF₂═CF—OCF ₂CF₂—SO₃Na and a number of byproduct-due small peaks at −78 to −85 ppm. It was found that the ratio [water-soluble fluorine-containing vinyl ether]:[byproducts] was 100:9. The aqueous solution obtained was evaporated to dryness; the product was readily crystallized and could be purified by recrystallization.

COMPARATIVE EXAMPLE 1

A 20-liter glass vessel equipped with a stirrer and a reflux condenser was charged with 6.4 kg of the fluorine-containing 2-alkoxypropionic acid derivative NaOC(O)CF(CF₃)OCF₂CF₂SO₃Na obtained in Production Example 1 and, as inert solvents, 17.7 kg of Cl(CF₂CFCl)₃Cl and 240 g of diethylene glycol dimethyl ether (3 parts by mass per 100 parts by mass of the fluorine-containing 2-alkoxypropionic acid derivative). The vessel was heated by means of a mantle heater. Upon arrival of the inside temperature at 180° C., the generation of CO₂ started. After 7 hours of heating under refluxing conditions (inside temperature 203° C.), the CO₂ generation suppressed and, therefore, the heating was discontinued. After cooling, the reaction mixture obtained was filtered, and the solid matter was washed with HCFC-225. The solid matter thus obtained was dissolved in water, and the insoluble sodium fluoride was filtered off to give an aqueous solution.

The thus-obtained aqueous solution was subjected to ¹⁹F-NMR spectrometry, and a comparison was made between the large peak at about −83.3 ppm (relative to CDCl₃) due to the underlined fluorine atoms of —OCF ₂CF₂— in the water-soluble fluorine-containing vinyl ether CF₂═CF—OCF ₂CF₂—SO₃Na and a number of byproduct-due small peaks at −78 to −85 ppm. It was found that the ratio [water-soluble fluorine-containing vinyl ether]:[byproducts] was 100:102. The aqueous solution obtained was evaporated to dryness; the product only became a thick syrup-like substance but could not be purified by recrystallization.

EXAMPLE 2

A 500-ml SUS stainless steel autoclave equipped with a reflux condenser was charged with the fluorine-containing 2-alkoxypropionic acid derivative NaOC(O)CF(CF₃)OCF₂CF₂SO₃Na (80 g) obtained in Production Example 1 and 130 g of ethyl acetate (163 parts by mass per 100 parts by mass of the fluorine-containing 2-alkoxypropionic acid derivative). The contents were heated to 145° C. by means of a heater and stirred. The CO₂ generated was discharged through the reflux condenser so that the autoclave inside pressure might be maintained at a level not exceeding 0.1 MPa. After 5 hours, no increase in inside pressure was observed any longer, so that the autoclave was allowed to cool. All the internal gas was discharged at around room temperature. The reaction mixture was filtered, and the filtrate was concentrated under reduced pressure to give a white solid. The solid obtained was subjected to ¹⁹F-NMR spectrometry, whereby it was confirmed that the water-soluble fluorine-containing vinyl ether CF₂═CF—OCF₂CF₂—SO₃Na was the main product ([water-soluble fluorine-containing vinyl ether]:[byproducts] =100:9).

EXAMPLE 3

A 300-ml SUS 316 stainless steel autoclave was charged with 81 g of the fluorine-containing 2-alkoxypropionic acid derivative NaOC(O)CF(CF₃)OCF₂CF₂SO₃Na obtained in Production Example 1 and 88 g of tetrahydrofuran (109 parts by mass per 100 parts by mass of the fluorine-containing 2-alkoxypropionic acid derivative). The contents were heated to 140° C. by means of a heater and stirred for 3 hours. The autoclave inside pressure arrived at a maximum of 1.4 MPa. The autoclave was allowed to cool, and all the internal gas was discharged at around room temperature. The reaction mixture was filtered, and the filtrate was concentrated under reduced pressure to give a white solid. The solid obtained was subjected to ¹⁹F-NMR spectrometry, and it was confirmed that the water-soluble fluorine-containing vinyl ether CF₂═CF—OCF₂CF₂—SO₃Na was the main product ([water-soluble fluorine-containing vinyl ether]:[byproducts] =100:11).

INDUSTRIAL APPLICABILITY

The method for producing a water-soluble fluorine-containing vinyl ether according to the present invention, which has the constitution described above, makes it possible to obtain water-soluble fluorine-containing vinyl ethers in good yields from the corresponding fluorine-containing 2-alkoxypropionic acid derivatives. 

1. A method for producing a water-soluble fluorine-containing vinyl ether which comprises subjecting a fluorine-containing 2-alkoxypropionic acid derivative represented by the following general formula (I):

 (wherein A represents —OM¹ or —OM² _(1/2), and M¹ represents an alkali metal and M² represents an alkaline earth metal; X represents a halogen atom; Y¹ and Y² are the same or different and each represents a fluorine atom, a chlorine atom, a perfluoroalkyl group or a fluorochloroalkyl group; n represents an integer of 0 to 3, and n atoms/groups of Y¹ may be the same or different; m represents an integer of 1 to 5, and m atoms/groups of Y² may be the same or different; and Z represents a hydrophilic group) to thermal decomposition at a temperature of not lower than 50° C. but lower than 170° C. in the presence of a coordinating organic solvent comprising one or both of ethyl acetate and tetrahydrofuran to give a water-soluble fluorine-containing vinyl ether represented by the following general formula (II):

 (wherein Y¹, y², Z, n and mare as defined above), said coordinating organic solvent having a coordinating property with an ion of said M₁ or an ion of said M² and said coordinating organic solvent being in an amount of 10 to 1,000 parts by mass per 100 parts by mass of said fluorine-containing 2-alkoxypropionic acid derivative.
 2. The method for producing a water-soluble fluorine-containing vinyl ether according to claim 1, wherein the hydrophilic group is —COOM³, —OS0 ₃M³, —SO₃M³, —O₂PM³, —OP(OM³)₂, —O₂P(OM³), —OPO(OM³)₂, —PO₂(OM³), —PO(OM³)₂, —COOM⁴ _(1/2), —OSO₃M⁴ _(1/2), —OSO₃M⁴ _(1/2), —SO₃M⁴ _(1/2), —O₂PM⁴ _(1/2), —OP(OM⁴ _(1/2))₂, —O₂P(OM⁴ _(1/2)), —OPO(OM⁴ _(1/2))₂, —PO₂(OM⁴ _(1/2)), —PO(OM⁴ _(1/2))₂, or a substituted ammonio group forming a salt with a conjugate base of an inorganic acid or fatty acid (its substituents being two or three alkyl groups which are the same or different), wherein M³ represents an alkali metal, a hydrogen atom or NR¹R²R³R⁴ in which R¹, R², R³ and R⁴ are the same or different and each represents a hydrogen atom or an alkyl group containing 1 to 4 carbon atoms, and M⁴ represents an alkaline earth metal.
 3. The method for producing a water-soluble fluorine-containing vinyl ether according to claim 1, wherein the thermal decomposition is carried out at a temperature not lower than 50° C. but lower than 150° C.
 4. The method for producing a water-soluble fluorine-containing vinyl ether according to claim 1, wherein the coordinating organic solvent is in an amount of 30 to 300 parts by mass per 100 parts by mass of the fluorine-containing 2-alkoxypropionic acid derivative.
 5. The method for producing a water-soluble fluorine-containing vinyl ether according to claim 1, wherein the coordinating organic solvent comprises an aprotic polar organic solvent.
 6. The method for producing a water-soluble fluorine-containing vinyl ether according to claim 5, wherein the aprotic polar organic solvent is an ether solvent, sulfolane, hexamethylphosphoric triamide, acetonitrile, dimethylformamide, dimethyl sulfoxide, ethyl acetate and/or tetramethylurea.
 7. The method for producing a water-soluble fluorine-containing vinyl ether according to claim 6, wherein the ether solvent is a glyme-based solvent, a diethyl ether, a diisopropyl ether, tetrahydrofuran, dioxane, anisole and/or a crown ether.
 8. The method for producing a water-soluble fluorine-containing vinyl ether according to claim 7, wherein the glyme-based solvent is dimethoxyethane, diethoxyethane, monoethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol monomethyl ether and/or diethylene glycol monoethyl ether.
 9. The method for producing a water-soluble fluorine-containing vinyl ether according to claim 5, wherein the aprotic polar organic solvent is a glyme-based solvent.
 10. The method for producing a water-soluble fluorine-containing vinyl ether according to claim 5, wherein the aprotic polar organic solvent has a water content not exceeding 250 ppm.
 11. The method for producing a water-soluble fluorine-containing vinyl ether according to claim 5, wherein the aprotic polar organic solvent is diethylene glycol dimethyl ether.
 12. The method for producing a water-soluble fluorine-containing vinyl ether according to claim 11, wherein the diethylene glycol dimethyl ether has a water content not exceeding 250 ppm.
 13. The method for producing a water-soluble fluorine-containing vinyl ether according to claim 1, wherein the fluorine-containing 2-alkoxypropionic acid derivative represented by the general formula (I) has a water content not exceeding 0.1% by mass.
 14. The method for producing a water-soluble fluorine-containing vinyl ether according to claim 1, wherein n is 0 or
 1. 15. The method for producing a water-soluble fluorine-containing vinyl ether according to claim 2, wherein Z is —SO₃M³ or —SO₃M⁴ _(1/2).
 16. The method for producing a water-soluble fluorine-containing vinyl ether according to claim 2, wherein Z is —SO₃M³, A is —OM¹ or —OM² _(1/2), Y¹ is a trifluoromethyl group, Y² is a fluorine atom and m is
 2. 17. The method for producing a water-soluble fluorine-containing vinyl ether according to claim 16, wherein n is
 0. 18. The method for producing a water-soluble fluorine-containing vinyl ether according to claim 1, wherein the coordinating organic solvent comprises at least one solvent with a boiling point not higher than a temperature of the thermal decomposition reaction. 